Food allergies, of which the most common is cows' milk allergy, are caused, in most cases, by a reaction to the proteins in the food. In the early years of life the immune system is still developing and may fail to recognise and tolerate such dietary proteins. The result is that the baby or child or young animal treats the dietary protein as a foreign substance and develops an allergic response to it. Food allergies may affect not only humans but also other mammals such as dogs and cats.
Usually, food hypersensitivity appears just after a susceptible baby, child or young animal first encounters a new food. The first dietary proteins generally encountered by human babies at least are cows' milk proteins and, as noted above, cows' milk allergy is the most common food allergy. It is generally accepted that babies with established cows' milk allergy have an increased risk of developing allergies to other dietary proteins such as egg and cereal proteins but even those babies who have successfully developed oral tolerance to cows' milk proteins may subsequently develop allergies to other dietary proteins such as egg and cereal proteins when these are introduced into the diet at weaning.
From a dietary point of view there are two ways to treat an established allergy—either foods containing the allergen must be avoided altogether, or the foods must be treated to eliminate their allergenic potential, for example by extensive hydrolysis. Infant formulas containing extensively hydrolysed cows' milk proteins (peptides consisting of not more than five amino acids) are manufactured for this latter purpose.
Infant formulas containing less extensively hydrolysed cows' milk proteins have been proposed to help reduce the risk of developing cows' milk allergy, particularly for children thought to be at risk of the same (that is, children having at least one close family member who suffers from an allergy). Such products, are often described as hypoallergenic which term is defined in European Directive 96/4/EC in the context of milk as containing hydrolysed proteins the allergenicity of which is at least 100 times less than that of the unhydrolysed proteins. One process for the production of hypoallergenic cows' milk proteins is described in U.S. Pat. No. 5,039,532
Many other approaches have been proposed to reduce the allergenicity of cows' milk proteins but by comparison with this, relatively little attention has been paid to other dietary proteins which frequently provoke allergic reactions such as egg proteins. Eggs are an excellent source of high quality proteins which typically account for about 12% by weight of the edible part of the egg. Eggs may not only be consumed in their native state for example as boiled or poached eggs or omelettes for example but they are also frequently used as ingredients in other foodstuffs for both nutritional and functional purposes. For example, eggs may be used as colourants and binding agents in dishes such as pasta and as thickening and gelling agents in dishes such as puddings, quiches and sauces.
However, the egg protein ovalbumin in particular has been linked to the development of allergy. Indeed, reduction of allergenicity of egg proteins may be an even greater need then reduction of allergenicity of cows' milk proteins given that allergy to cows' milk proteins usually disappears spontaneously between the age of two and five years whereas allergy to egg proteins is generally slower to disappear and may even persist throughout life. It is therefore an object of the present invention to provide a process for producing hypoallergenic egg proteins as well as novel food products containing hydrolysed egg proteins.